As processor-based devices continue to proliferate, user interfaces are often provided to allow a user to interact with the device. For example the user interface may allow a user to adjust operating characteristics and to select features of the device made available for user control and selection by software executed by the device's processor. In any event, a user interface requires some means for a user to navigate through the user interface to indicate desired user selections. Such a navigation device can be as simple as a keypad, or as advanced as a three-dimensional motion stage.
In a large number of processor-based devices, such as personal computers (PCs) in particular, a graphical user interface (GUI) is employed. In devices employing a GUI, there is typically a need to provide a navigation device which can indicate a user's desire to move a reference point (e.g., a cursor) across the GUI. Known navigations devices include: a trackball, a touchpad, a joystick, a touchscreen, a scrollwheel, a THINKPAD® pointer, a mechanical mouse having a mouse ball and rollers, and a so-called “optical mouse.”
Each of these navigation devices has its benefits, but they all also have certain limitations.
For example, trackballs tend to be large and bulky. Also, these devices get dirty and when that happens, then they perform poorly.
The mechanical mouse has been perhaps the most widely employed navigation device for PCs which employ a GUI. These devices are relatively inexpensive to manufacture and easy to use. However, perhaps even more than trackballs, these devices also get dirty and then they perform poorly.
As a result, the optical mouse has become more widely deployed in recent years. There are several variations of the optical mouse, including LED or laser illumination, imaging features directly or looking at speckle reflections, etc. However all of these devices detect relative movement of the device based on light reflected from a “mouse pad” or other reference surface along which the optical mouse is moved to an image sensor. As a result, like a mechanical mouse, the optical device requires a reference surface along which it moves. Furthermore, in the case of the optical mouse, certain surfaces—such as clean glass—will not work.
What is needed, therefore, is a navigation device that may avoid some of the disadvantages of the devices discussed above. In particular, it would be desirable to provide a navigation device that is less prone to impaired operation due to dust and small dirt particles. It would also be desirable to provide a navigation device that can operate on clean glass. It would further be desirable to provide a navigation device that can operate in free-space without any reference surface.